There are quite a few suitable ones available for less than $500. Check,   http://www.needledoctor.com/Phono-Preamps . They have just about the largest selection on phono preamps you'll find anywhere.

Worth noting:

Pro-Ject Tube Box S $449 (I'm a tube fan, works with MM and MC cartridges)

Clearaudio Nano $400 (works with MM and MC cartridges)

Vincent Audio PHO-8 $400 (nice two box unit with separate power supply, works with MM and MC cartridges)

All three of these work with both MM and MC cartridges. This is a plus in my book. If you ever want to replace that M97 with something better you will be able to consider a MC cartridge.

Although I have a Shure V-15IV with a Jico SAS stylus I prefer either my re-tipped Ortofon MC-20 Super or Sumiko Blackbird. Both of them are MC cartridges and IMO sound better than the Shure. The Shure is a better tracker especially at low tracking force.